Difference Between Alloy Steel and Carbon Steel

Main Difference – Alloy Steel vs Carbon Steel

Steel industry is one of the largest industries in the world. Steel is made primarily by mixing iron with other metal or non-metal elements. The purpose of the production of steel is to obtain different properties by mixing iron with other elements. Alloy steel and carbon steel are two types of steel which differ from each other due to their composition. The main difference between alloy steel and carbon steel is that alloy steel has high amounts of other elements apart from iron and carbon whereas carbon steel has trace amounts of other elements apart from iron and carbon.

Key Areas Covered

1. What is Alloy Steel
     – Definition, Properties, Uses
2. What is Carbon Steel
     – Definition, Properties, Uses
3. What is the difference between Alloy Steel and Carbon Steel
     – Comparison of Key Differences

Key Terms: Alloy Steel, Carbon, Carbon Steel, Iron, Steel

What is Alloy Steel

Alloy steel are metal alloys of iron, carbon and high amounts of other elements. The other elements present in it typically includes manganese, silicon, nickel, titanium, copper, and chromium. These elements are called alloy elements because these elements are mixed together to form an alloy. The purpose of adding these elements is to improve the properties of steel. Alloy steel can be divided into two categorize as follows.

• Low Alloy Steel
• High Alloy Steel

Low alloy steels contain a low amount of alloy elements whereas high alloy steels contain a high amount of alloy elements. Normally, alloy elements are added in order to improve the hardness and durability of the steel. Alloy steel are also corrosion resistant due to the presence of considerable amounts of other elements such as chromium.

For example, stainless steel is an alloy steel. It contains about 10% of chromium along with iron and carbon in the mixture of elements. Due to its corrosion resistant property, stainless steel is used to manufacture kitchen items.

Figure 1: A swing check valve made of stainless steel (alloy steel).  

What is Carbon Steel

Carbon steel is composed of iron and carbon. Alloy elements are present in trace amounts. Some of these elements are silicon, manganese, sulfur and phosphorous. Carbon steel is also divided into two groups as below.

• High Carbon Steel
• Low Carbon Steel

Due to the high amount of carbon present in carbon steel, it shows properties such as hardness, less ductility, reduced weldability, and low melting point. Mild steel is a type of low carbon steel having about 0.05% to 0.25% of carbon. Due to its high iron content, it is corrosive in moist environments. High carbon steels contain about 0.6% to 1.0% of carbon. These high carbon steel are very strong. Therefore, carbon steels are used as building materials.

Figure 2: Carbon Steel used as a building material

Difference Between Alloy Steel and Carbon Steel

Definition

Alloy Steel: Alloy steel is a type of steel having a high percentage of other elements apart from iron and carbon.

Carbon Steel: Carbon steel is a type of steel having a high amount of carbon and low amounts of other elements.

Corrosion Resistance

Alloy Steel: Alloy steels are corrosion resistant.

Carbon Steel: Carbon steels are less resistant to corrosion.

Strength

Alloy Steel: The strength of alloy steel is low compared to carbon steel.

Carbon Steel: Carbon steel has a high strength.

Weldability

Alloy Steel: Weldability of alloy steel is high. 

Carbon Steel: Weldability of carbon steel is low.

Melting Point

Alloy Steel: Alloy steels have high melting points.

Carbon Steel: Carbon steels have low melting points.

Ductility

Alloy Steel: The ductility of alloy steel is high.

Carbon Steel: Ductility of carbon steel is low.

Conclusion

The composition of elements in steel differs from one type of steel to another. Therefore, steels are categorized mainly according to their composition. Alloy steel and carbon steel are such two types of steel. The main difference between alloy steel and carbon steel is that alloy steel has high amounts of other elements apart from iron and carbon whereas carbon steel has trace amounts of other elements apart from iron and carbon.

References:

1.“Carbon Steels and Alloy Steels Information.” Carbon Steels and Alloy Steels Information | Engineering360. N.p., n.d. Web. Available here. 16 June 2017. 
2.”Alloy Steel.” Metal Supermarkets N.p., n.d. Web. Available here. 16 June 2017. 

Image Courtesy:

1. “Stainless steel swing check valve” by Goodwin Steel Castings (CC BY-SA 2.0) via Flickr
2. “Stratford Station roof support” By Heather Smith – The Alloy Valve Stockist’s photo gallery. (CC BY 3.0) via Commons Wikimedia